The wallet came with a fake Social Security card with a preprinted Social Security number on it, empty spaces where the name and birthdate would go, and the word SPECIMEN stamped across it. When these people died, their next of kin opened the wallet and pulled out the card. They gave the social security number on the card to the person who filled out their loved one's death certificate. [Link]

The number wasn't arbitrarily chosen: a wallet company executive used the SSN of his secretary, Mrs. Hilda Schrader Whitcher.